Seed XOR Changes

XOR from Seed Vault (select other parts of the XOR from seeds in the vault). This allow Restore of geographically distributed SeedXOR, without physically bringing the parts together.
(Q only) Seeds, for SeedXOR, can be scanned from SeedQR instead of typing them by hand.

Multisig Changes

Now possible to disable BIP-67 compliance (sorted pubkeys) by importing a descriptor with multi() clause. This needs to be enabled—opt-in only. BIP-67 has been the standard for almost 10 years, so we don’t expect many to use this feature.
JSON wrapped imports to provide custom name instead of the filename. Most useful for USB and NFC imports which have no filename.
Descriptor checksum is no longer required on import. If provided, must be correct.
(Q only) Create an Airgapped Multisig Wallet (a.k.a using CC as multisig coordinator) now works with BBQRs, in addition to MicroSD cards.

libsecp256k1 bumped to latest version: 0.5.0 (point multiplication algorithm speed up, etc).
Speed improvements in our signature grinding for positive R.
Update to libsecp256k1, plus our optimizations, yield 30% improvement in signing speed over previous version. Improvement is 15% in overall signing speed, as signatures are only part of process (UTXO validation & change checks take time).
Security: Improve side-channel protection: libsecp256k1 context randomization now happens before each signing session.

Bugfix: Do not allow import of multisig wallet when same keys are shuffled.
Bugfix: Do not read whole PSBT into memory when writing finalized transaction (performance).
Bugfix: Prevent user from restoring Seed XOR when number of parts is smaller than 2.
Bugfix: Fix display alignment of Seed Vault menu.
Bugfix: Properly handle null data in OP_RETURN.
Bugfix: Do not allow lateral scroll in Address Explorer when showing single address from custom path.

New Feature: Seed XOR can be imported by scanning SeedQR parts.
New Feature: Input backup password from QR scan.
New Feature: (BB)QR file share of arbitrary files.
New Feature: Create Airgapped now works with BBQRs.
Change: Default brightness (on battery) adjusted from 80% to 95%.
Bugfix: Properly clear LCD screen after BBQR is shown.
Bugfix: Writing to empty slot B caused broken card reader.
Bugfix: During Seed XOR import, display correct letter B if own seed already added to the mix.
Bugfix: Stop re-wording UX stories using a regular expression.
Bugfix: Fixed “easy exit” from quiz after split Seed XOR.